Articulating constant force finishing tool actuator

ABSTRACT

An apparatus for maintaining constant force engagement between a finishing tool and a workpiece. The apparatus includes a biasing device that can be coupled to a robotic manipulator, and a support arm having a tool holder disposed at one end. The biasing device is actuated by a pressure source to cause the support arm to rotate a finishing tool into engagement with a workpiece. A counterweight disposed on a second end of the support arm offsets the mass of the finishing tool, whereby constant force engagement between the finishing tool and workpiece may be maintained as the finishing tool is articulated to move relative to the workpiece.

FIELD OF THE INVENTION

[0001] The present invention pertains generally to apparatus forfinishing manufactured goods, and more particularly to an apparatus formaintaining a constant force between a finishing tool and a workpiece.

BACKGROUND OF THE INVENTION

[0002] In the manufacture or restoration of various products, it isoften desirable to perform a finishing operation, such as buffing,grinding or polishing. For example, in the manufacture or restoration offine jewelry, it is often desired to buff precious metal components toachieve a fine finish for aesthetic appearance. During such finishingoperations, it is generally important not to apply excessive pressure ofthe finishing tool against the workpiece, which would otherwise causeunwanted excessive removal of material from the workpiece. Optimally, itis desired to maintain contact between the workpiece and the finishingtool at a known and constant force.

[0003] Prior devices for maintaining a constant force between afinishing tool and a workpiece have typically involved complexmechanical devices, often incorporating electronic controls and feedbacksystems. The complexity of these prior devices presents an increasedlikelihood of malfunctioning and makes them expensive to purchase andmaintain, often to the point that use of the devices is prohibitive foreconomic reasons. By way of example, an automated finishing system mightutilize a programmable computer-controlled robotic arm to engage aworkpiece against a stationary finishing tool with a constant force.Such a configuration generally requires some type of force feedback toan appropriately programmed controller, as well as complicatedprogramming code necessary to manipulate the robotic arm to engage theworkpiece with a constant force. The time, effort, and equipmentnecessary to achieve the desired result of constant force finishing withthis type of system is likely to increase the cost to an extent that useof such a device is prohibited in many applications.

[0004] In some applications, however, it may be desired to move afinishing tool over a workpiece to finish a large area of the workpiece,or to finish multiple surfaces on a workpiece. When several pieces ofthe same type of workpiece are to be finished in this manner, suchfinishing operations are particularly suited to use of a roboticmanipulator to articulate the finishing tool over the appropriatesurfaces of the workpiece. The problem remains to ensure that thefinishing tool is maintained in contact with the workpiece at a constantforce without requiring complicated programing of the roboticmanipulator or complex devices such as those described above.

[0005] There is thus a need for a simple apparatus for maintaining aconstant force between a finishing tool and a workpiece wherein thefinishing tool may be articulated over the workpiece by a roboticmanipulator and wherein the apparatus overcomes drawbacks of the priorart, such as those described above.

SUMMARY OF THE INVENTION

[0006] The present invention provides an apparatus for supporting afinishing tool on a robotic manipulator and for maintaining a constantforce between the finishing tool and a workpiece as the roboticmanipulator articulates to move the finishing tool relative to theworkpiece. Advantageously, the apparatus maintains constant forceengagement between the finishing tool and the workpiece withoutrequiring complex feedback systems or special programing of the roboticmanipulator.

[0007] In one aspect of the invention, the apparatus includes a biasingdevice that is couplable to the operative end of a robotic manipulator.A support arm is rotatably coupled to the biasing device and has a toolholder at one end for supporting a finishing tool. The biasing device isconfigured to move the support arm toward the workpiece, such that thefinishing tool engages the workpiece with a constant force as therobotic manipulator articulates to move the finishing tool over thesurface of the workpiece.

[0008] In another aspect of the invention, the biasing device includes arotary actuator having an output shaft coupled to the support arm. Theoutput shaft is caused to rotate with a constant torque, whereby thesupport arm rotates to move the finishing tool into engagement with theworkpiece. As the finishing tool moves over the workpiece, the constanttorque applied to the support arm maintains constant force engagementbetween the finishing tool and the workpiece.

[0009] In an exemplary embodiment, the rotary actuator is actuable by asource of pressurized air. In another exemplary embodiment, the rotaryactuator is a rotary hydraulic device actuable by pressurized hydraulicfluid. Pressure regulators coupled between the actuators and thepressure sources ensure that the torque of the output shaft is keptconstant. The rotary actuator may comprise a rack-and-pinionarrangement, or it may be a vane-type rotary device.

[0010] The features and objectives of the present invention will becomemore readily apparent from the following Detailed Description taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and, together with a general description of the inventiongiven above, and the detailed description given below, serve to explainthe invention.

[0012]FIG. 1 is a perspective view of an articulating constant-forcetool actuator according to the present invention;

[0013]FIG. 2 is a perspective view of the tool actuator of FIG. 1,depicted in various positions relative to the workpiece;

[0014]FIG. 3 is a cross-sectional view of the tool actuator depictingexemplary components; and

[0015]FIG. 4 is a cross-sectional view similar to FIG. 3, illustratinganother exemplary apparatus according to the present invention.

DETAILED DESCRIPTION

[0016] Referring to FIG. 1, there is shown an exemplary apparatus 10 formaintaining a constant force engagement between a finishing tool 12 anda workpiece 14 while the finishing tool 12 is articulated to move alongat least one surface of the workpiece 14. The apparatus 10 includes abiasing device 16 which may be connected to the operative end 18 of arobotic manipulator 20. The robotic manipulator 20, is programmed orcontrolled, as known in the art, to move the finishing tool 12 tovarious positions and/or locations relative to the workpiece 14.

[0017] The apparatus 10 further includes a support arm 22 coupled to thebiasing device 16 and extending outwardly from the biasing device 16.The finishing tool 12, such as a buffing, grinding, or polishing wheel,is disposed on a first end of the support arm 22 and is coupled to thesupport arm 22 by a tool holder 26. The finishing tool 12 may be drivenby a motor (not shown) mounted directly on the support arm 22, adjacentthe finishing tool 12, or alternatively mounted on another portion ofthe apparatus 10 and driven, for example, by a belt, as known in theart. While the finishing tool 12 has been depicted in the exemplaryembodiment herein as a disk or wheel coupled to the support arm 22 forrotational movement, it will be understood by those of ordinary skill inthe art that the finishing tool 12, tool holder 26 and motor may havevarious other configurations for finishing a workpiece 14 as known inthe art. As a non-limiting example, the finishing tool 12 may be coupledto a motor for vibratory, orbital, or oscillatory motion.

[0018] Advantageously, the biasing device 16 is configured to move thesupport arm 22 to engage the finishing tool 12 against the workpiece 14at a constant force. In the exemplary embodiment shown, the biasingdevice 16 rotates the support arm 22 in the direction of arrow 28, suchthat an edge 30 of the finishing tool 12 engages the workpiece 14. Whilethe apparatus 10 has been depicted here in a configuration wherein thesupport arm 22 is biased to move in a single rotational direction, itwill be recognized that the biasing device 16 may alternatively beconfigured to rotate the support arm 22 in both directions.

[0019] Because the robotic manipulator 20 may be programmed to move tovarious locations within a three-dimensional coordinate system, therobotic manipulator 20 may be used to move the finishing tool 12relative to the workpiece 14 while the biasing device 16 maintainsconstant force engagement between the finishing tool 12 and theworkpiece 14, as best depicted in FIG. 2. In FIG. 2, the apparatus 10 isdepicted in a first position P1 in engagement with a first surface 40 ofthe workpiece 12. In this position, the robotic manipulator 20 may movethe finishing tool 12 along the first surface 40 of the workpiece 14 ina direction indicated by arrow 42. FIG. 2 also depicts the apparatus 10in a second position P2 in engagement with a second surface 44 of theworkpiece 14 wherein the robotic manipulator 20 may be articulated tomove the finishing tool 12 along the second surface 44 of the workpiece14 in the direction of arrow 46. The apparatus 10 is also depicted in athird position P3 wherein the finishing tool 12 is in engagement with athird surface 48 of the workpiece 14 and whereby the robotic manipulator20 may be articulated to move the finishing tool 12 along the thirdsurface 48 of the workpiece 14 as indicated by directional arrow 50.While only three different positions of the apparatus are depicted inFIG. 2, it will be recognized by those of ordinary skill in the art thatthe robotic manipulator may be articulated to cause the finishing toolto engage various other surfaces of the workpiece, or to be moved invarious linear or curvilinear motions while the biasing device maintainsthe finishing tool in constant force engagement with the workpiece.

[0020] Referring to FIGS. 1 and 2, the apparatus 10 further includes acounterweight 60 provided on a second end 62 of the support arm 22 tooffset the mass of the tool holder 26 and the finishing tool 12 disposedon the first end 24 of the support arm 22. In the exemplary embodimentshown, the counterweight 60 is adjustable to slide along the support arm22, whereby the counterweight 60 may be adjusted to accommodate variousfinishing tools which may be selectively coupled to the tool holder 26at the first end 24 of the support arm 22. Alternatively, thecounterweight 60 may also be selected or adjusted to accommodate theweight of a motor or other components or devices supported at the firstend 24 of the support arm 22. Advantageously, the counterweight 60offsets the mass of the finishing tool 12 and other components at thefirst end 24 of the support arm 22, whereby the biasing device 16 isable to maintain constant force engagement between the finishing tool 12and the workpiece 14 while the robotic manipulator 20 articulates tomove the finishing tool 12 to various positions on the workpiece 14.Specifically, the adjustable counterweight 60 accounts for the mass loadof these components as the apparatus 10 is articulated such that thesupport arm is biased in a direction of the gravitational loading ofthese components without the need for complex force actuators orfeedback mechanisms.

[0021] Referring now to FIG. 3, there is shown a cross-sectional viewdepicting an exemplary embodiment of a biasing device 16 according thepresent invention. The biasing device 16 comprises a rotary actuator 70having rack and pinion gears 72, 74 operatively coupled to at least onepiston member 76 and disposed within a housing 78. The housing 78 ismounted to the operative end 18 of the robotic manipulator 20 by amounting plate 80. An output shaft 82 coupled to the pinion gear 74extends from the housing 78 and is coupled to the support arm 22 by asecond mounting plate 84. A rotary bearing 86 is coupled between thehousing 78 and the second mounting plate 84 whereby rotation of theoutput shaft 82 is transferred to the support arm 22 to move the supportarm 22 in the direction of rotation of the output shaft 82. The rotarybearing 86 may be a cross-roller bearing, or any other suitable bearingcapable of supporting an axial load while permitting rotation of supportarm 22. In the exemplary embodiment shown, an outer race 88 of therotary bearing 86 is secured by fasteners 90 to the housing 78, and thesecond mounting plate 84 is secured by fasteners 90 to an inner race 92of the rotary bearing 86. Rolling elements 94 between the outer andinner races 88, 92 allow the second mounting plate 84 to rotate with theoutput shaft 82, whereby support arm 22 coupled to mounting plate 84also rotates with output shaft 82.

[0022] In use, pressurized air or hydraulic fluid is supplied to therotary actuator 70 to cause the pistons 76 to move in a desireddirection, thereby rotating the shaft 82 and support arm 22.Advantageously, the pressure of the pressurized air or hydraulic fluidsupplied to the rotary actuator 70, is controlled by a pressureregulator (not shown) such that the support arm 22 is moved to engagethe finishing tool 12 with the workpiece 14 at a constant force.

[0023]FIG. 4 depicts another exemplary biasing device 16 a according tothe present invention, wherein components similar to those in FIGS. 1-3have been similarly numbered. In this embodiment, the biasing device 16a is a vane-type rotary actuator configured to operate under the actionof pressurized fluid provided to the rotary actuator via fluid inlet andoutlet ports 100, 102. In the exemplary embodiment shown, the rotaryactuator includes a vane 104 disposed within housing 78 and coupled tooutput shaft 82, whereby the output shaft 82 is caused to rotate underthe action of the pressurized fluid, as known in the art.

[0024] While the present invention has been illustrated by thedescription of the various embodiments thereof, and while theembodiments have been described in considerable detail, it is notintended to restrict or in any way limit the scope of the appendedclaims to such detail. Additional advantages and modifications willreadily appear to those skilled in the art. The invention in its broaderaspects is therefore not limited to the specific details, representativeapparatus and methods and illustrative examples shown and described.Accordingly, departures may be made from such details without departingfrom the scope or spirit of Applicant's general inventive concept.

What is claimed is:
 1. An apparatus for maintaining constant forceengagement between a finishing tool and a workpiece, the apparatuscomprising: a biasing device couplable to a robotic manipulator forarticulation about and along at least two orthogonal axes relative tothe workpiece; a support arm extending from said biasing device andhaving an inner end operatively coupled to said biasing device formovement in at least two orthogonal directions toward the workpiece, andhaving a distal end; and a tool holder disposed on a distal end of saidsupport arm and configured to support the finishing tool; said biasingdevice configured to move said support arm to engage the finishing toolagainst the workpiece at a constant force.
 2. The apparatus of claim 1,wherein said biasing device comprises: a rotary actuator having anoutput shaft; and a bearing assembly operatively coupled to said supportarm and engaging said output shaft, whereby rotation of said outputshaft moves said support arm to engage the workpiece with a constantforce.
 3. The apparatus of claim 1, further comprising a counterweightdisposed on said support arm, generally opposite said tool holder, tooffset the mass of said tool holder and the finishing tool supported bysaid support arm.
 4. The apparatus of claim 2, wherein said rotaryactuator comprises: at least one piston member actuatable by a pressuresource; a rack gear coupled to said piston for movement in response toactuation of said piston; and a pinion gear coupled to said output shaftand engaging said rack gear, whereby actuation of said piston causessaid output shaft to rotate.
 5. The apparatus of claim 2, wherein saidrotary actuator includes at least one vane coupled to said output shaft,whereby said output shaft is rotated by placing said vane incommunication with a source of pressurized fluid.
 6. The apparatus ofclaim 1, further comprising a robotic manipulator adapted to be coupledto said biasing device and to articulate said biasing device, saidsupport arm, and said tool holder relative to the workpiece while saidbiasing device moves said support arm to engage the finishing toolagainst the workpiece at a constant force.